1. Field of the Invention
The invention relates to a method and a control system for controlling an auxiliary device of a vehicle, wherein the auxiliary device can be automatically started at a starting time which is determined based on an estimated departure time of the vehicle. In particular, the invention relates to an air-conditioning device which can be automatically started for pre-air-conditioning (PAC) based on an estimated departure time of an electric and/or hybrid vehicle.
2. Description of the Related Art
In electric vehicles, the maximum cruising distance of the vehicle is limited due to the limited capacity of the batteries. If air-conditioning equipment is employed while cruising, this air-conditioning equipment consumes energy which is therefore not available for driving. As a result, the maximum cruising distance is shortened due to the employment of the air-conditioning equipment.
It may be possible to employ pre-air-conditioning (PAC) while the vehicle is connected to an external power supply for battery charging. The pre-air-conditioning is started at a programmable starting time prior to an estimated departure time of the electric vehicle. The pre-air-conditioning cools or heats the passenger cabin of the vehicle while the vehicle is connected to the battery charger such that the air-conditioner draws the energy from the battery charger connection and not from the battery. As a consequence, the passenger cabin is air-conditioned at the time of departure and the amount of energy consumed by the air-conditioning equipment while the vehicle is driving may be reduced. As a result, the maximum cruising distance may be increased.
However, it is a difficult task to estimate the optimum starting time of the operation of the air-conditioning device because the departure time is often unknown. Even if the driver is commuting, the basically periodical use of the vehicle may be disturbed by irregular events. The starting time of the pre-air-conditioning can be determined within an ordinary timer control. The driver may specify his departure time manually in advance and the vehicle starts the pre-air-conditioning operation accordingly.
The starting time of the pre-air-conditioning operation may also be directly programmed by the driver. However, it may be inconvenient for the driver to manually specify the departure time and/or the starting time of the pre-air-conditioning prior to every driving. If the starting time of the pre-air-conditioning is not correctly determined, the energy may be employed in an ineffective way. If the pre-air-conditioning is started too early, the air-conditioning equipment operates for an interval which is too long and therefore uses too much energy or stops after a pre-determined fixed time and the temperature in the vehicle will go back to the initial temperature so that the inputted energy is wasted, while on the other hand, a too short period of pre-air-conditioning may result in an incorrect temperature at the departure time. These problems will lead to the necessity of using valuable battery power of the vehicle after its departure. Similar problems may occur in vehicles having programmable seat-heaters or an auxiliary heating often used in countries with a colder climate.
From a more general point of view, the problem may relate to any auxiliary device of a vehicle that consumes electrical power, where the starting time of the auxiliary device may depend on the departure time of the vehicle. For example, a vehicle driver might want to synchronize his vehicle multimedia files, e-mails etc. with the data from his home network shortly before leaving with his car. Although in non-electric vehicles the battery power issue is not as crucial as in electric vehicles, an incorrect timer programming may result in either a loss of energy or in a reduction of comfort.
The document JP 2007-269161 A teaches an air-conditioner control device which starts an air-conditioning device using a statistical approach based on a frequency function. This device, however, cannot react to changes in the driver's habits, e.g. if he departs later or earlier as usual etc.